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可再生木质素基功能材料的制备及应用研究
梁凤兵
2016-05
Keyword木质素 羧酸化 重金属吸附剂 磁性炭 非均相芬顿催化剂
Subject Area天然高分子材料
Subtype专题报告
Other AbstractLignin, the second most abundant biopolymer on earth, is one of renewable natural biomass resources. In China, industrial lignin mainly existed in the waste liquor from the paper and pulping industry has the properties of rich sources, low price and poor water solubility. Using industrial lignin as raw material, producing environmentally friendly green fine chemical products via chemical modification and developing green chemical processes not only reduce the pollution damage to the environment caused by the pulping waste liquor, but also increase the economic value added of industrial lignin, which has double significance in environment and resource. Firstly, lignin carboxylic acid derivatives (LCA) has been prepared by oxidation of lignin by dilute HNO3 and NaNO2 under mild conditions. In order to introduce a large number of hydrophilic carboxylic acid groups, the alcohol hydroxyl groups in the side of alkaline lignin were oxided to carboxylic acid without damaging the main structure of lignin. The results show that the lignin-based carboxylic acid was produced under the optimum conditions of nitric acid and lignin with mole ratio 8:1(the acid concentration is less than 1mol/L), nitrite and lignin with mole ratio 10:8, reaction time of 24h, reaction temperature of 20℃. The structure and properties of lignin-based lignin-based carboxylic acid has been characterized by elemental analysis , FT-IR, GPC, NMR and Boehm titration. The results show that in the lignin carboxylic acid derivatives, the carboxylic acid content is 3.4mmol/g, and the total acidic groups reach 4.1 mmol/g. Furthermore, the main frame structure of lignin molecule has been preserved in the process of synthesis. The adsorption performances of heavy metals (Cr(III), Cu(II), Pb(II) and Cd(II)) onto LCA have been investigated. The effects of pH, concentration of heavy metal ions, and contact time on adsorption have been studied using batch experiments. The results suggest that the adsorption behavior of metal ions on LCA is dependent on the above three factors. Langmuir and Freundlich models were applied to describe the adsorption of metal ions on LCA. Langmuir and Freundlich isotherms exhibit good fit to the experimental adsorption data, and the maximum adsorption capacities of LCA for the four metals are in the following order: Cd(II) >Pb(II) >Cr(III)≫Cu(II). Moreover, the metal-loaded LCR can be easily regenerated and reused by a simple acid treatment with the desorption efficieny above 95%. Secondly, for resource utilization of the used adsorbent, the Fe-loaded lignin carboxylic acid are used as the raw materials for preparation of lignin-based magnetic carbon (LMC) by calcination method, developing the new route of value-added utilization of lignin. The effect of Fe2+ concentration, immersion time, calcining temperature, and calcining time on the structure and catalytic activity of LMC has been investigated. The results showed that optimal conditions for preparation of LMC were: Fe2+ concentration 107 mmol/L, impregnation time 4 h, calcination temperature 900 ℃, calcination time 2 h. The surface morphology and phase composition of LMC were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). The results show that the calcination temperature and calcination time have the important effect on the catalytic activity of LMC , and there are many kinds of iron oxides in the LMC microporous materials, such as FeO, Fe2O3, Fe3O4 and FeOOH. LMC can be used as a heterogeneous Fenton catalysts for catalytic degradation of dyeing wastewater. The catalytic degradation of the simulated dye wastewater of RhB has been studied used LMC as heterogeneous catalyst, and the effect of pH, LMC dosage, H2O2 concentration and dye concentration has been investigated. The results show that the suitable degradation conditions for the dyeing wastewater were pH value 3, catalyst concentration 1 g/L, hydrogen peroxide concentration 8.56 mmol/L, RhB solution initial concentration 100 mg/L. The degradation rate of RhB is nearly 100% within 15 minutes under these optimal conditions. The recyclability of LMC catalyst was also tested. Only slightly decrease in activity was observed after the catalyst was recycled five times, and the dissolved iron ion concentration in aqueous solution was lower than pollutant emission limit value for industrial wastewater in EU, indicating that LMC can function as a stable catalyst.
Abstract木质素作为自然界第二丰富的天然高分子聚合物,是一种可再生的天然生物质资源。在我国,工业木质素主要来自于碱法制浆造纸废液,具有来源丰富、价格低廉和水溶性差等特点。以工业木质素为原料,通过化学改性生产“环境友好”的绿色精细化工产品以及开发绿色化学工艺,不仅可以减少造纸废液造成的环境污染,也可以提高工业木质素的经济附加值,充分利用木质素这类重要生物质资源,具有环境和资源双重意义。 本研究利用稀硝酸-亚硝酸盐体系在尽量不破坏木质素本体骨架结构的情况下氧化木质素侧链中醇羟基生成羧基,在碱木质素分子中引入大量亲水性羧酸基团,合成了木质素羧酸衍生物。采用硝酸用量为木质素用量的8倍(且酸浓度≤1mol/L)、亚硝酸盐用量为木质素用量的0.8倍、反应时间24h、反应温度20℃的反应条件可得到优化合成工艺。利用元素分析、红外光谱分析、核磁共振、凝胶渗透色谱等分析手段对木质素羧酸衍生物产物进行了结构表征,结果表明:木质素羧酸衍生物中羧基含量为3.4mmol/g,总酸量高达4.7 mmol/g,且木质素分子的主体骨架结构在合成过程中较完整的保存下来。 以自制木质素羧酸为吸附剂,直接用于吸附溶液中四种重金属阳离子(Cr(III)、Cu(II)、Pb(II)和Cd(II))。结果表明:pH值、重金属离子浓度和吸附时间均对木质素羧酸吸附剂的吸附过性能有显著影响,提高溶液pH和重金属离子浓度、延长吸附时间均有利于重金属离子的吸附;Langmuir和Freundlich吸附等温模型均能良好描述木质素羧酸吸附剂对Cr(III)、Cu(II)、Pb(II)和Cd(II)四种重金属离子的吸附行为,对它们的qm分别为143.885 mg/g、62.93 mg/g、161.031 mg/g、168.350 mg/g,是一种吸附性能良好、成本低廉的吸附剂;木质素羧酸吸附剂对Cu(II)、Cr(III)、Pb(II)和Cd(II)四种重金属离子具有良好的解吸再生能力和可重复使用性,且解吸效率维持在95%以上。 通过将木质素羧酸衍生物在铁离子溶液中搅拌浸渍,得到负载铁的木质素碳化前驱体,然后再经过高温碳化制备得到木质素基磁性(LMC)。结果表明:在浸渍工序中,浸渍溶液中Fe2+离子浓度、浸渍时间对铁改性木质素碳化前驱体的制备影响显著,适宜的铁改性木质素碳化前驱体的制备条件为:木质素羧酸用量3.4g、100ml 107mmol/L的Fe2+溶液、浸渍时间4h;在碳化工序中,碳化温度和碳化时间对所制备的木质素基磁性炭材料的结构和催化性能影响重大,适宜的碳化条件为:氮气保护下,碳化温度900℃,碳化时间2h。利用SEM、XRD、XPS和BET等对LMC结构和催化活性,发现:在适宜条件下制备得到木质素磁性炭为微孔结构,表面均匀分布着种铁氧化物颗粒(FeO、 γ-Fe2O3、 Fe3O4和 α-Fe2O3)和铁单质,对罗丹明B的催化降解活性较高,可作为易分离、高效的非均相芬顿催化剂使用。 以木质素基磁性炭作为非均相芬顿催化剂,考察了其对模拟染料废水-罗丹明B水溶液的催化降解反应条件。结果表明:初始pH、催化剂浓度、过氧化氢浓度、罗丹明B初始浓度等因素均会影响木质素基磁性炭非均相Fenton催化氧化反应效果;适宜的催化降解反应条件:pH值为3.0,催化剂浓度为1 g/L,过氧化氢浓度为8.56 mmol/L,罗丹明B溶液初始浓度为100 mg/L。此外,木质素基磁性炭催化剂具有良好的重复使用性能和稳定性。因此,木质素基磁性炭在有机废水处理过程中可被广泛应用,具有很高的使用价值。
Document Type研究报告
Identifierhttp://ir.qibebt.ac.cn/handle/337004/9801
Collection生物基材料组群
Affiliation中科院青岛生物能源与过程研究所
Recommended Citation
GB/T 7714
梁凤兵. 可再生木质素基功能材料的制备及应用研究. 2016.
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